The U.S. Supreme Court upheld the Cross-State Air Pollution Rule (CSAPR), which is an Environmental Protection Agency (EPA) measure designed to limit nitrogen oxide (NOx) and sulfur dioxide (SO2) emissions from power plants.

The Supreme Court’s action reversed an August 2012 ruling from the U.S. Court of Appeals for the District of Columbia Circuit that vacated the regulation, which was originally set to take effect Jan. 1, 2012, and remanded it to the EPA.

By the time CSAPR was first expected to take effect in 2012, the economic incentive from low natural gas prices already had led to increased gas burn, investments in new gas plants, and coal plant retirements, according to analysis from Bentek Energy. At the time, that same analysis showed that this incentive led to a reduction of emissions and resulted in many states meeting CSAPR’s emissions targets, despite the rule itself being suspended.

Bentek’s analysis of the latest data from the EPA’s continuous emissions monitoring system (CEMS) shows that if emissions annual targets remain the same as in the original rule, CSAPR alone will have a limited impact on overall fuel competition or market share.

All impacted states with annual SO2 and NOx targets under the rule already are compliant with 2012 allowances, and many are also compliant with 2014 targets.

Other key takeaways from Bentek’s analysis include:

Bentek’s GenCast data shows that 11 of 23 states affected by the rule already are compliant with CSAPR’s 2014 SO2 budgets. Planned coal plant retirements in the next three years will bring an additional four states within compliance by 2017, with another two, Ohio and Illinois, within 2 percent and 9 percent of their baseline SO2 budgets by then.

SO2 and NOx emissions from power generation have fallen 32 percent and 14 percent since 2011, respectively, in states with available allocations that are affected by the EPA’s CSAPR mandates. Low natural gas prices in recent years have enabled utilities to burn more gas and rapidly approach compliance with the rule.

Scrubbers at coal plants have helped cut emissions, but a key factor has been the increased use of natural gas, with gas market share of generation in 2013 up 3 percent from 2011 at the expense of coal.